Self-pulsing oscillator



Dec. 23, 1947 2 H. w. LORD 2,433,282

SELF-PULSING OSCILLATOR Filed April 27. 1945' 20 2| 22 22a 24 L l4. sgggcgz o; g I 7 voLTs Inventor:

Harold W Lord, 7

His Attorney. 7

Patented Dec. 23, 1947 SELF-PULSING OSCILLATOR Harold W. Lord, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application April 27, 1945, Serial No. 590,584

9 Claims. 1

My invention relates to pulse generating cir-- cuits and, more particularly, to self-pulsing oscillator circuits of the type employed in connection with pulse transmitters and the like.

It is a general object of my invention to provide a new and improved self-pulsing oscillator which at once employs a minimum ofequipment and is capable of producing pulses of considerable power.

It is a further object of my invention to provide, in a self-pulsing oscillator circuit, a nonoscillatory pulse generating circuit of the multivibrator type in which one of the multivibrator tubes is used also as the oscillator tube.

It is a still further objectof my invention to provide new and improved non-oscillatory means for definitely determining the conductive interval of a self-pulsing oscillator.

It is another object of my invention to provide a self-pulsing oscillator in which all discharge devices are normally cut off so that the duty cycle upon all devices is very low.

In accordance with my invention, a triggered pulse generating circuit of the normally non-comductive multivlbrator type shown in my copending application, Serial No. 587,689, filed April 11, 1945, is connected so that the triggered discharge device produces high frequency oscillations during the pulse intervals. In this type of multivibrator circuit, the triggered pulser tube is regeneratively connected so that output pulses are abruptly built up and abruptly terminated, thereby to render the output pulses substantially rectangular in shape. The other discharge device conducts only momentarily in delayed response to initiation of conduction in the pulser tube and by its conduction impresses upon the pulser tube a shut-oil impulse of short duration. The duty cycle on both tubes is thus very low. In the selfpulsing oscillator arrangement of the subject application, the pulser tube is regeneratively coupled for high frequency oscillations independently of the non-oscillatory pulse generating circuit.

The features of my invention which 'I believe to be novel are set forth with particularity in the appended claims. Th invention itself, both as to its organization. and manner of operation, to gether with further objects and advantages there,-. of, may best be appreciated by referring now to the following detailed specification taken in con,- junction with the accompanying drawing the single figure of which is a schematic circuit dia-v gram of a self-pulsing oscillator embodying my invention.

The oscillator circuit illustrated in the drawing comprises an electron discharge device I having an anode 2, a cathode}, and a control electrode 4. In order to produce oscillations of predetermined frequency, there is employed a tuned oscillatory feedback circuit of any desired type. In the a g. I have sho a modified Ha tley osc lator circuit comprising a pair or inductors 5 and 6 connected in series circuit relation by a pair or blocking capacitors 1 and 8. The capacitors l and prevent oscillator frequency currents from flowing through the non-oscillatory pulse generatin circuit to be described hereinafter, The inductors 5, 6 and the capacitors "l, g are shunted by a tuning capacitor 9. The resonant circuit thus formed is connected at one side to the anode 2 of the discharge device I and at the other side to the control electrode 4. The mid-point between the capacitors I, 8 is connected to ground, and the cathode 3 of the discharge device I is grounded through a cathode resistor I0. Anode potential positive with respect to ground is supplied to the oscillator tube I from a suitable source of unidirectional current supply l3+ through an anode resistor II. It will be understood by those skilled in the art that the circuit above described oscillates in a well-known manner, the coupling between the anode-to-cathode and control electrode-to-cathode circuits being sufiicient to provide the necessary regenerative feedback.

The pulse generating circuit for alternately rendering the oscillator tube I. conductive and non-conductive at predetermined intervals comprises the discharge device I. a, transformer I2, and a second discharge device IS. The discharge device I3 includes an anode I4,- a cathode l5, and a control electrode IB, and is utilized only to provide cutsofi' impulses for the oscillator tube I. The cathode I5 is grounded and anode potential is supplied to the anode II from the positive potential source B+ through an anode resistor I9.

The pulse transformer I2 has three windings 20, 2|, and 22, the windings 20 and 2| being connected to provide regenerative feedback between the anode 2 and control electrode 4 of the oscillator device I independently of the tuned oscillator feedback circuit, and the winding 2-2 providing 7 delayed positive impulses to initiate conduction in the shut-off tube I3. The transformer winding 2| is connected at one end to ground, and at the other end to the anode'Z of the discharge device I through a coupling capacitor 23 and the inductor 5. The capacitor 1 lay-passes the ungrounded end of the winding 2 I to ground for high frequency currents. The ungrounded end of the transformer winding 2| is also connected to the control 3 electrode I6 of the discharge device I3 through a timing capacitor 24, and to the positive potential source B+ through'a current limiting resistor 25 for polarization of the core. One end of the transformer winding 20 is connected through a resistor I! to a suitable source of unidirectional potential negative with respect to ground andindicated upon the drawing at C. The other end of the winding 20 is connected through the inductor 6 to the control electrode 4 of the discharge device I. grid connection to ground potential for high frequencies. A damping resistor 26 1s connected across the terminals of the transformer winding 20. The source C- is by-passcd to ground for high frequencies through a capacitor I8. The transformer winding 22 is similarly connected at one end to the potential source C and at the other end through a resistor 2! to the control electrode I6 of the discharge device I3. The winding 22 is by-passed for high frequency currents by a capacitor 22a. The transformer windings 28, 2|, and 22 are so arranged upon the core that adjacent ends of the windings, as shown on the drawing, are of like polarity.

Triggering potential is supplied to the pulse generating circuit from a suitable source 29 of negative triggering impulses through a capacitor The capacitor 8 Icy-passes this 7 33 to the ungrounded terminal of the transformer winding 2I. Shut-off impulses are fed back from the discharge device I3 to the oscillator tube I through a coupling capacitor 28 between the anode I4 of the device I3 and the control electrode 4 of the tube I.

I wish to have it understood that, while I-have shown by way of illustration a modified Hartley circuit connected to control high frequency oscillations in the discharge device I, my invention is not necessarily limited to such an oscillator circuit, but that if desired any preferred type of oscillator coupling may be used between the anode and control electrode of the discharge device I. For example, if desired, a resonant cavity type of oscillator may be employed.

In operation, negative triggering. impulses are supplied from the source 29 of trig er potential to the ungrounded end of the transformer winding 2|. The triggering impulses initiate, at this end of the transformer winding, recurrent negasaturation, but rather the transformer I2 is so adjusted and damped that, in combination with the tuned grid circuit 5, 6, 9, it permits the grid voltage to stabilize at an optimum bias value for oscillation. Indeed, the resistor I I in the grid pulsing circuit of the device I may so load the grid 4 that the bias potential maintained on the grid is negative throughout the oscillatory interval.

To ensure definite termination of the pulse of oscillations across the anode resistor II at a desired time, the discharge device I3 is employed to provide shut-01f impulses. The discharge device I3 is normally non-conductive by reason of the negative bias derived from the source C- through the transformer winding 22 and the resistor 21. As soon as conduction is initiated in the discharge device I, the negative potential maintained at the ungrounded end of the transformer winding 2I by pulse conduction through the discharge device I drives the control electrode I6 of the discharge device I3 more than normally negative by reason of the coupling through the capacitor 24, thereby to maintain the discharge device I3 non-conductive without increasing the charge upon the capacitor 24. The negative pulse across the winding 2 I, however, induces in the winding 22 a similar pulse of such polarity that it tends to reverse the charge upon the timing capacitor 24 thereby to drive the control electrode I6 of the discharge device I3 positive. Reversal of the charge upon the capacitor 24 in response to the induced pulse across the transformer winding 22 is delayed exponentially by the characteristics of the RC circuit including the capacitor 24 and the resistor 21. After a predetermined time delay, however, the positive pulse across the transformer winding 22 overcomes the negative potential maintained upon the control electrode I6 from the negative source C- and by coupling through the capacitor 24, so that the discharge device I3 is rendered conductive. As soon as the discharge device I3 conducts, the potential of its anode I4 decreases abruptly, and the negative pulse thus formed is coupled through the capacitor 28 to the control electrode 4 of the oscillatory discharge device I. The capacitors I8 and 28 and the resistor II provide an alternatin current output circuit for the device I3. When the control electrode 4 is driven negative by conduction in the discharge device I3, conduction in the discharge device I is abruptly terminated. As soon as the anode current of the discharge device I begins to decrease, regerenation through the charge device I becomes conductive, the anode I potential decreases, thereby to drive the ungrounded end of the transformer winding 2I further negative by coupling through the capacitor 23, so that the control electrode 4 is driven further positive by regeneration through the transformer windings 20 and 2I. In this manner, the discharge device I is driven rapidly to a condition of maximum conduction, so that the pulse of oscillations across the anode resistor II has a very sharp leading edge. Thus; regeneration through the transformer I2 maintains the discharge device I in a state of oscillation for a predetermined period which may be longer than the duration of the triggering impulses from the source 29. The maximum conduction condition in the oscillator tube I is preferably not at current transformer windings 20 and 2I aids in the abrupt termination of conduction in the discharg device I. Additional regeneration is provided through the discharge device I3, for as soon as the poten-- tial of the anode 2 increases the grid I6 is driven more positive by coupling through the capacitor 24. This increases conduction in the discharge device I3 and thus increases the negative potential impressed upon the grid 4 by coupling through the capacitor 28.

As soon as the oscillator tube I cuts off, the negative voltage pulse across the transformer winding 2| is terminated, thereby to terminate the positive voltage puls across the transformer winding 22 so that the negative bias source C- It will now be evident that the pulse duration of the oscillations appearing across the anode resistor H is determined solely by the characteristics of the RC circuit 24, 21 so that, by change in the capacity of the capacitor 24, the duration of the pulsed oscillations may be controlled. Moreover, regeneration through the transformer windings 20 and 2| is effective both upon initiation and termination of the oscillations of the discharge device I, so that substantially rec tangular pulses of oscillations are formed. It will also be evident that, by providing a pulse generator of the multivibrator type in which both discharge devices are normally non-conductive, the oscillator tube being combined with one of the multivibrator tubes and the other tube being conductive only instantaneously to provid shut-off impulses, a minimum of equipment, in addition to the oscillator tube itself, is required.

It will be evident to those skilled in the art that the accuracy of timing may be increased, if desired, by substituting for the timing capacitor 24 an open ended artificial transmission line section, as described in my foregoing copending application,

While I have described only a preferred embodiment of my invention by Way of illustration, many modifications will occur to those skilled in the art, and I, therefore, wish to have it understood that I intend in the appended claims to cover all such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, a direct current source, an oscillator energized from said source and comprising a first electron discharge device having an anode, a cathode and a control electrode, an anode-cathode circuit for said discharge device, oscillator coupling means for deriving from said anode-cathode circuit and supplying to said control electrode oscillatory energy in proper phase to support oscillations in said circuit, a second electron discharge device, means normally maintaining both said discharge devices non-conductive, means for recurrently rendering said first discharge device conductive thereby to initiate oscillations therein, time element means responsive to initiation of conduction in said first discharge device for rendering said second discharge device conductive, and means substantially instantaneously responsive to conduction in said second discharge device for rendering said first discharge device non-conductive thereby to term-inate oscillations therein.

2. In combination, a direct current source, an oscillator energized from said source and comprising a first electron discharge device having an anode, a cathode and a control electrode, an anode-cathode circuit for said discharge device, oscillator coupling means for deriving from said anode-cathode circuit and supplying to said control electrode oscillatory energy in proper phase to support oscillations in said circuit, a second electron discharge device, means for normally maintaining both said discharge devices nonconductive, triggering means for rendering said first discharge device conductive to initiate oscillations therein, time element means responsive to initiation of conduction in said first discharge device for rendering said second discharge device conductive, and means responsive to conduction in said second discharge device for causing both said devices to return rapidly to nonconductive condition.

3. In combination, a direct current source, an oscillator energized from said source and comprising a first electron discharge device having an anode, a cathode and a control electrode, an anode-cathode circuit for said discharge device, oscillator coupling means for deriving from said anode-cathode circuit and supplying to said control electrode oscillatory energy in proper phase to support oscillations in said circuit, a second electron discharge device, biasing means for normally maintaining both said discharge devices non-conductive, a source of triggering potential impulses arranged recurrently to overcome the bias of said first discharge device thereby to render said first discharge device conductive and initiate oscillations therein, regenerative means independent of said oscillator coupling means for maintaining said first discharge device conductive independently of said triggering source, time ele ment means energized by said regenerative means for rendering said second discharge device conductive a predetermined time after initiation of oscillations in said first discharge device, and means substantially instantaneously responsive to conduction in said second discharge device for terminating said oscillations.

4. In combination, a direct current source, an oscillator energized from said source and comprising a first electron discharge device having an anode, a cathode and a control electrode, an anode-cathode circuit for said discharge device, oscillator coupling means for deriving from said anode-cathode circuit and supplying to said control electrode oscillatory energy in proper phase to support oscillations in said circuit, a second electron discharge device having an anode, a cathode and a control electrode, biasing means normally maintaining both said discharge devices non-conductive, a source of triggering potential impulses connected to render said first discharge device conductive, regenerative coupling means independent of said oscillator coupling means and including a transformer connected between the anode and control electrode of said first discharge device, time element means energized from said transformer and arranged to overcome the bias of said second discharge device a predetermined time after each initiation of conduction in said first discharge device, and coupling means substantially instantaneously responsive to conduction in said second discharge device for rendering said first discharge device non-conductive.

5. A self-pulsing oscillator comprising a pair of electron discharge devices having anodes, cathodes and control electrodes, a source of ne ative biasing potential arranged normally to maintain both said discharge devices non-conductive, an oscillatory tuned circuit regeneratively coupling the anode and control electrode of one of said discharge devices to support oscillations therein, a three-winding transformer having one Winding coupled to each of said control electrodes and a third winding coupled to the anode of said first discharge device, said transformer providing non-oscillatory regenerative coupling independent of said oscillator coupling between the anode and control electrode of said first discharge device, a source of negative triggerin impulses coupled to the anode of said first discharge device to render said device conductive and thereby to initiate oscillations, means comprising a timing capacitorand discharge resistor for energizing the control electrode of said second discharge device from said transformer so as to overcome the bias of said second discharge device gradually in response to initiation of conduction in said first discharge device, and means substantially instantaneously responsive to conduction in said second discharge device for terminating said oscillations.

6. A self-pulsing oscillator comprising a pair of electron discharge devices, means normally maintaining both said discharge devices non-conductive, oscillator coupling means connected to one of said discharge devices for supporting oscillations therein, triggering means for supplying a potential impulse to said one discharge device to render it conductive and to initiate oscillations therein, time element means responsive to initiation of said conduction in said first discharge device for rendering the second of said discharge devices conductive after a predetermined interval, means responsive to conduction of said second device for returning said first device to non-conductive condition, and means responsive to termination of conduction in said first device for rendering said second discharge device nonconductive.

7. A self-pulsing oscillator comprising a pair of electron discharge devices having input and output circuits, a tuned circuit regeneratively coupling the input and output circuits of one of said discharge devices to support oscillations therein, separate non-oscillatory means regeneratively coupling the input and output circuits of said one. discharge device, means for normally maintain-. ing both said devices non-conductive, a source of triggering impulses arranged recurrently to render said one discharge device conductive thereby to initiate oscillations therein, time element means including said non-oscillatory coupling means and the second discharge devicefor terminating said oscillations a predetermined time after their initiation, and means responsive to termination of conduction in said one discharge device for rendering said second discharge device non-conductive.

8. A self-pulsing oscillator comprising a pair of electron discharge devices having input and'output circuits, a tuned circuit regeneratively coupling the input and output circuits of one of said discharge devices to support oscillations therein, separate non-oscillatory means regeneratively coupling the input and output circuits of said one discharge device, means-for normally maintaining both said discharge devices non-conductive, a source of triggering impulses arranged recurrently to render said one discharge device conductive thereby to initiate oscillations therein, time element means energized by said nonoscillatory coupling means and arranged gradually to overcome the bias of the second discharge device thereby to render said second discharge device conductive a predetermined time after initiation of oscillations in said first discharge device, and. means instantaneously responsive to conduction in said second discharge device for terminating said oscillations.

9. In combination, a pair of electron discharge devices having input and output circuits, biasing means arranged normally to maintain both said discharge devices non-conductive, oscillatory coupling means for deriving from the output circuit and supplying to the input circuit of one of said discharge devices oscillatory energy in proper phase to support oscillations therein, second coupling means rendering said discharge devices alternatively conductive, a source of triggering impulses connected recurrently to render said one discharge device conductive, time delay means responsive to initiation of conduction in said one discharge device for momentarily disabling said second coupling means after a predetermined time thereby to render the other of said discharge devices conductive, and means responsive to termination of conduction in said one discharge device for rendering said other discharge device non-conductive.

HAROLD W. LORD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,922,195 Brown Aug. 15, 1933 2,181,568 Kotwski Nov. 28, 1939 2,294,411 Lay Sept. 1, 1942 2,333,688 Shepard Nov. 9, 1943 

